This program is concerned with serveal phases of the general problems related to the renin-angiotensin-aldosterone system and electrolyte metabolism in hypertension and congestive heart failure. The specific areas include: 1) the pathogenesis of experimental renal hypertension, 2) the pathogenesis of spontaneous hypertension in the rat, 3) the control of renin secretion, 4) the control of aldosterone secretion, and 5) the physiology of congestive heart failure. The methods include: 1) experimental surgical procedures for the production of renal hypertension, right heart failure, left heart failure, and thoracic inferior vena cava construction with ascites, and 2) chemical and assay methods for adrenal steroids and renin. Renin is quantified by radioimmunoassay of angiotensin I. Aldosterone, corticosterone, cortisol and desoxycorticosterone are measured by the double isotope derivative assay and, in addition, aldosterone and corticosterone are measured by radioimmunoassay. Electrolytes and kidney function are studied by classical methods including flame photometry, renal clearances of Cr and PAH and electromagnetic flowmeters. Cardiac output will be measured by dye dilution and aortic flow with an electromagnetic flowmeter. Regional renal blood flow is measured by the microsphere method.